Forecasters are going to be busy over the next two to three weeks as an active pattern becomes even more volatile and could eventually mean significant snow to parts of New England. The rain this weekend is the initial play of this stormy pattern, in spite of our being on the warm side of this storm.

El Nino is still a dominant force, but two other players on the global weather stage have shifted their positions, and where they are standing now tends to bring more cold and snow.

The first player is the arctic oscillation (AO) index, which is crashing into negative territory. The image below shows not only has the AO gone negative, but is falling to very low levels This negative side of the index means the polar vortex is weakening, and, in turn, the arctic air is spilling south from the poles. Parts of Europe are feeling the brunt of this arctic air right now, but eventually pieces of it will impact us here in southern New England.

The icy air will impact the Midwest with below-zero air and very low wind chill this weekend. The Seattle Seahawks-Minnesota Vikings wild-card playoff game will take place with temperatures in the teens and wind chills near zero. That isn’t as cold as New Year’s Eve 1967 when it was 13 below zero for a Packers-Cowboys game on Lambeau Field. The wind chill approached 50 below during the game.

The North Atlantic Oscillation has also gone into negative territory. When this index becomes negative, the jet stream tends to buckle in such a way as to bring an increase in storms on the East Coast.

With the AO and the NAO both negative, it’s only a matter of time before there’s a big hit of snow. The question forecasters will be grappling with in the coming two weeks: Which part of the country is going to get it?

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